Image guided awl/tap/screwdriver

ABSTRACT

A trackable medical instrument for use in a computer assisted image guided medical and surgical navigation systems that generate images during medical and surgical procedures, includes a guide member having an emitter array for being tracked by the system and a drive shaft contained within the guide member having a proximal and a distal end, the drive shaft being rotatable within the guide member while being fixable axially inside the guide member, the proximal end of the drive shaft having a first connector for interchangeably receiving at least one drive source, and the distal end having a second connector for interchangeably receiving at least one instrument tip.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to computer assisted imageguided medical and surgical navigation systems that generate imagesduring medical and surgical procedures indicating the relative positionof various body parts, surgical implants, and instruments. Inparticular, the present invention relates to an instrument for use in animage guided surgery navigation system that enables the system to trackboth the depth and the trajectory of the instrument during surgery.

2. Background of Related Art

Computer assisted image guided medical and surgical navigation systemsare known and used to generate images in order to guide a doctor duringa surgical procedure. Such systems are disclosed, for example, in U.S.Pat. No. 5,383,454 to Bucholz; PCT application Ser. No. PCT/US94/04530(Publication No. WO 94/24933) to Bucholz; and PCT application Ser. No.PCT/US95/12984 (Publication No. WO 96/11624) to Bucholz et al.,incorporated herein by reference.

In general, these image guided systems use images of a body part, suchas CT scans, taken before surgery to generate images on a display, suchas a CRT monitor screen, during surgery for representing the position ofa surgical instrument with respect to the body part. The systemstypically include tracking devices such as, for example, an LED arraymounted on a surgical instrument as well as a body part, a digitizer totrack in real time the position of the body part and the instrument usedduring surgery, and a monitor screen to display images representing thebody and the position of the instrument relative to the body part as thesurgical procedure is performed.

There is a need in the art for a surgically navigable tool for use withthese image guided systems that is simple to use and manipulate, thatenables the computer tracking system to track both the trajectory of theinstrument and the depth that the instrument is inserted into the body,and that is easily interchangeable with alternative drive sources suchas a ratcheting handle or other instruments such as awls, taps, andscrewdrivers.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide an image guidedmedical instrument whose tip and trajectory can be simultaneouslytracked.

It is a further object of the invention to provide an image guidedmedical instrument capable of generating a signal representing thetrajectory and the depth of the tip of the instrument.

It is a still further object of the invention to provide an image guidedmedical instrument that may easily be used with any number of differenttips and handles.

It is another object of the invention to provide an image guided medicalinstrument that is of relatively simple construction and relatively easyto use.

Additional objects and advantages of the invention will be set forth inthe description which follows and, in part, will be obvious from thedescription or may be learned by practice of the invention. The objectsand advantages of the invention will be realized and attained by meansof the elements and combinations particularly pointed out in theappended claims.

To achieve the objects and in accordance with the purpose of theinvention, as embodied and broadly described herein, the inventioncomprises a trackable medical instrument for use in a computer assistedimage guided surgery system having a digitizer for tracking the positionof the instrument in three dimensional space and a display providing anindication of the position of the instrument with respect to images of abody part taken preoperatively. The instrument includes a guide memberhaving an emitter array mounted thereon for being tracked by thedigitizer, and a drive shaft contained within the guide member, thedrive shaft having a proximal and a distal end, the drive shaft beingrotatable within the guide member while being fixable axially within theguide member, the proximal end of the drive shaft having a firstconnector for interchangeably receiving at least one drive source, andthe distal end having a second connector for interchangeably receivingat least one instrument tip. The instrument may further include at leastone instrument tip for connection to the distal end of the drive shaftand a drive handle for connection to the proximal end of the drive shaftfor transmitting torque to the instrument tip to cause rotation of theinstrument tip.

In another aspect of this invention, the instrument may further includea sensor which senses the removal and the connection of an instrumenttip to the instrument. The sensor may be an electromechanical switch onthe guide member.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and arenot restrictive of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

FIG. 1 is a schematic front view of a computer assisted image guidedsurgery system used with an instrument according to the presentinvention.

FIG. 2 is a perspective view of an instrument according to the presentinvention.

FIG. 3 is an exploded view of the instrument shown in FIG. 2.

FIG. 4 is a view of a portion of the instrument shown in FIG. 2.

FIG. 5 is an exploded view of the portion of the instrument shown inFIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the present preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numbers areused in the drawings and the description to refer to the same or likeparts.

The medical instrument of the present invention is shown generally at 10in FIG. 1. Instrument 100 can be used in many known computer assistedimage guided surgical navigation systems such the system shown in FIG. 1and disclosed in PCT application Ser. No. PCT/US95/12984 (PublicationNo. WO 96/11624) to Bucholz et al., incorporated herein by reference. Acomputer assisted image guided surgery system, shown at 10, generates animage for display on a monitor 106 representing the real time positionof a body part and the position of instrument 100 relative to the bodypart.

An image may be generated on monitor 106 from an image data set storedin a controller, such as computer 108, usually generated preoperativelyby some scanning technique such as by a CAT scanner or by magneticresonance imaging. The image data set and the image generated havereference points for at least one body part. The reference points forthe particularly body part have a fixed spatial relation to theparticular body part.

System 10 also generally includes a processor for processing image data,shown as digitizer control unit 114. Digitizer control unit 114 isconnected to monitor 106, under control of computer 108, and toinstrument 100. Digitizer 114, in conjunction with a reference frame arc120 and a sensor array 110 or other known position sensing unit, tracksthe real time position of a body part, such as a cranium shown at 119clamped in reference frame 120, and an instrument 100. Reference frame120 has emitters 122 or other tracking means that generate signalsrepresenting the position of the various body reference points.Reference frame 120 is fixed spatially in relation to a body part by aclamp assembly indicated generally at 124,125, and 126. Instrument 100also has a tracking device shown as an emitter array 40 which generatessignals representing the position of the instrument during theprocedure.

Sensor array 110, mounted on support 112, receives and triangulates thesignals generated by emitters 122 and emitter array 40 in order toidentify during the procedure the relative position of each of thereference points and the instrument. Digitizer 114 and computer 108 maythen modify the image date set according to the identified relativeposition of each of the reference points during the procedure. Computer108 may then generate an image data set representing the position of thebody elements and the instrument during the procedure. System 10 mayalso include a foot switch 116 connected to instrument 100 and digitizer114 for controlling operation of the system. The structure and operationof an image guided surgery system is well known in the art and need notbe discussed further here.

Referring to FIGS. 2 and 3, an instrument according to the presentinvention is shown at 100. Instrument 100 includes a guide member 30, aninterchangeable instrument tip 15, and an interchangeable driving handle20.

A drive shaft 35 is housed within guide member 30 and is removablyconnected to an end, here the proximal end 37, to surgical instrumenttip 15 and at the other end, here the distal end 38, to driving handle20 such that torque applied manually or by motorized means to drivehandle 20 is transmitted to drive shaft 35 which in turn is transmittedto tip 15. Drive shaft 35, while it could be extractable such as forservice, is fixable axially in relation to guide member 30, but isrotatable within guide member 30. As shown in FIG. 5, bushings 33 may beprovided at each end of guide member 30 to ensure smooth motion betweendrive shaft 35 and guide member 30. Guide member 30 is preferably madeof stainless steel, but can also be made of titanium, aluminum orplastic. Shaft 35 is preferably made from stainless steel, titanium, oraluminum.

Instrument 100 further includes a tracking device such as emitter array40 attached to guide member 30 for tracking the location and trajectoryof instrument 100. As shown in FIG. 4, array 40 is equipped with aplurality of emitters or tracking means 45, preferably four emitters,for generating a signal representing the trajectory of instrument 100and the depth of instrument tip 15. Preferably emitters 45 are lightemitting diodes; however, other tracking devices known in the artcapable of being tracked by a corresponding sensor array are within thescope of the invention. For purposes of illustration, not limitation,the tracking device may generate signals actively such as with acoustic,magnetic, electromagnetic, radiologic, and micropulsed radar systems, orpassively such as with reflective surfaces.

Drive handle 20 and instrument tip 15 are shown as modular units thatcan be attached to drive shaft 35 with corresponding and interlockingmale and female socket joints. As shown in FIGS. 3 and 4, drive shaft 35has a female socket joint 34 for connection with a male socket 14 on tip15, and drive shaft 35 has a male socket joint 36 for connection with afemale socket joint 26 on drive handle 20. With the use of male andfemale socket joints, various instrument tips and various type and sizeddrive handles can be easily interchangeable. Instrument tip 15 could beany of a variety of instruments used in surgery such as taps, awls, andshaped tools for interacting with a work piece, such as a screwdriverfor driving screws. Drive handle 20 could be any number of existing orspecially designed handles and could be ratcheting, nonratcheting ormotorized. Instrument tip 15 and drive handle 20 could also bepermanently attached to drive shaft 35. Other suitable connection meansare within the scope of the invention as well.

In operation, torque applied to drive handle 20 is transmitted throughdrive shaft 35 to instrument tip 15. Because drive shaft 35 is fixedaxially in relation to guide member 30, guide member 30 can remainstationary while drive shaft 35 rotates without translating along theaxis of drive shaft 35. The relationship between array 40 and the axisof drive shaft 35, therefore, remains constant. Instrument tip 15 isalso fixed axially in relation guide member 30. As a result, therelationship between array 40 and instrument tip 15 also remainsconstant. Because the relationship between array 40 and tip 15 isconstant, the signals emitted by emitters 45 can be used by the computerassisted image guided surgical navigation system to inform the surgeonof the position of instrument 100, indicating both the trajectory ororientation in three dimensional space of instrument 100 and the lengthof travel along the trajectory, i.e., the depth instrument tip 15 hasbeen inserted into a body part.

It should be recognized that other variations or modifications may bemade to provide an instrument that has an emitter array fixed axiallyrelative to the instrument tip while allowing the instrument tip torotate relative to the emitter array. For example, guide member 30 mayalso be integral with instrument tip 15 and/or drive handle 20. Thearray could then be fixed axially relative to the instrument and meanscould be provided to allow rotation of the instrument relative to thearray.

As discussed above, a variety of different instrument tips may be easilyinterchanged on instrument 100. To use these different instrument tips,information concerning the dimensions of the different tips may beentered into computer 108. As a result, computer 108 can process thevarious image data for the specific instrument tip being used so thatsystem 10 tracks the depth of the tip being used or, in the case of ascrewdriver, so that system 10 tracks the depth of the screw beinginserted.

System 10 may also be provided with a mechanism to prevent the systemfrom operating after a new tip has been connected until computer 108 hasbeen recalibrated. For example, an electromechanical switch, or othersuitable sensors, could be provided on instrument 100 to provide asignal to computer 108 indicating that instrument tip 15 has beenremoved from instrument 100 or that a new instrument tip 15 has beencoupled to instrument 100. The switch is preferably a micro switch butcan be embodied by any suitable electrical or electromechanical deviceor sensing device capable of providing a signal in response toattachment or detachment at a particular point on guide member 30 or tip15.

The switch may be automatically actuated when tip 15 is removed orcoupled to instrument 100. Computer 108 may be operably connected to theswitch, such as through cable 161, and is responsive to the operation ofthe switch. Alternatively, if a wireless instrument is used such as onewith passive reflective surfaces in place of LED emitters, any suitableform of communication known in the art can be used. An alarm or otherindication of some type, such as a message or display on monitor 106,may be generated by computer 108 indicating to the user that tip 15 hasbeen changed. The computer 108 may further prevent the system fromoperating until the system has been recalibrated for the new instrumenttip. Recalibration may be accomplished by touching the instrument tip toa known reference point. Recalibration of the instrument tip can bepositively confirmed by means of a light emission from the emitter array40 detected by sensor array 110 and triangulated to determine theposition of the instrument tip. Alternatively, the dimensions of theinstrument or tool type may be entered into computer 108 or selectedfrom a pre-programmed list of tool dimensions or tool types. Further,recalibration could be accomplished by a fiber optic device for readinga bar code on the instrument tip, or by any other suitable recalibrationtechnique.

It will also be apparent to those skilled in the art that variousmodifications and variations can be made to the structure andmethodology of the present invention without departing from the scope orspirit of the invention. In view of the foregoing, it is intended thatthe present invention cover modifications and variations of thisinvention provided they fall within the scope of the following claimsand their equivalents.

1. A trackable medical instrument for use in a computer assisted imageguided surgery system having a digitizer for tracking the position ofthe instrument in three dimensional space and a display providing anindication of the position of the instrument with respect to images of abody part take taken preoperatively, the instrument comprising: a guidemember having an emitter array mounted thereon for being tracked by adigitizer; and a drive shaft contained within the guide member, thedrive shaft having a longitudinal axis and a proximal and a distal end,the drive shaft being rotatable within the guide member while beingfixable within the guide member in a direction of the longitudinal axis,the proximal end of the drive shaft having a first connector forinterchangeably receiving at least one drive source for transmittingtorque to the drive shaft causing rotation of the drive shaft relativeto the guide member, and the distal end having a second connector forinterchangeably receiving at least one instrument tip.
 2. The instrumentaccording to claim 1, further comprising at least one instrument tip forremovable connection to the distal end of the drive shaft.
 3. Theinstrument according to claim 2, wherein the at least on one drivesource comprises a drive handle for removable connection to the proximalend of the drive shaft for transmitting torque to the drive shaft andthe instrument tip to cause rotation of the instrument tip.
 4. Theinstrument according to claim 3, wherein the drive handle and the driveshaft include a male-female socket joint to removably connect the driveshaft to the drive handle.
 5. The instrument according to claim 3,wherein the drive handle includes a ratchet.
 6. The instrument accordingto claim 3, wherein the drive handle includes a motor for impartingtorque to the drive shaft.
 7. The instrument according to claim 2,wherein the instrument tip and the drive shaft include a male-femalesocket joint to removably connect the drive shaft to the instrument tip.8. The instrument according to claim 2, wherein the instrument tip is anawl.
 9. The instrument according to claim 2, wherein the instrument tipis a tap.
 10. The instrument according to claim 2, wherein theinstrument tip has a shaped end for mating with a workpiece to berotated by said drive shaft.
 11. The instrument according to claim 2,wherein the instrument tip is a drill bit.
 12. The instrument accordingto claim 1, wherein the emitter array includes at least one LED arrayfor emitting light signals.
 13. The instrument according to claim 12,wherein the LED array includes a base and a plurality of LED emittersdisposed on the base.
 14. The instrument according to claim 1, whereinat least one bushing is provided in the guide member to reduce frictionbetween the guide member and drive shaft.
 15. The instrument accordingto claim 1, wherein the instrument includes a sensor which senses theremoval and connection of an instrument tip to the instrument.
 16. Theinstrument according to 15, wherein the sensor includes anelectromechanical switch on the guide member electrically connected tothe system.
 17. A trackable medical instrument for use in a computerassisted image guided surgery system having a digitizer for receivingsignals representing a position of the instrument during surgery, acomputer for processing the signals received, and a display forproviding an image representing the position of the instrument in threedimensional space during surgery, the instrument comprising: guidingmeans for guiding the instrument in three dimensional space, the guidingmeans including signaling means for providing a signal representing thetrajectory of the instrument and the location of the instrument; anddriving means for driving the instrument contained within the guidingmeans, the driving means having a longitudinal axis and being fixable inrelation to the guiding means in a direction of the longitudinal axiswhile being rotatable in relation to the guiding means, the drivingmeans having a first end adapted to interchangeably receive at least onemedical instrument tip and an opposite end adapted to interchangeablyreceive at least one drive source.
 18. The instrument according to claim17, wherein the instrument includes a sensing means for sensing theremoval and the connection of an instrument tip to the instrument. 19.The instrument according to 18, wherein the sensing means includes anelectromechanical switch on the guiding means connected to the a meansfor processing.
 20. The instrument according to claim 17, wherein theguiding means comprises a housing for receiving the driving means, thedriving means being rotatable within the housing while being retainedaxially within the housing.
 21. The instrument according to claim 20wherein the signaling means comprises an LED array.
 22. The instrumentaccording to claim 21, further comprising an instrument tip forconnection to the first end of the driving means.
 23. The instrumentaccording to claim 22, further comprising a drive handle for connectionto the opposite end of the driving means for transmitting torque to theinstrument tip to cause rotation of the instrument tip.
 24. Theinstrument according to claim 20, wherein the driving means comprises adrive shaft having mating connectors on both ends for connection tocorresponding connectors disposed on an instrument tip and a drivesource.
 25. The instrument according to claim 24, wherein at least onebushing is provided between the housing and the drive shaft to reducefriction between the guide handle and drive shaft.
 26. The instrumentaccording to claim 22, wherein the instrument tip is an awl.
 27. Theinstrument according to claim 22, wherein the instrument tip is a tap.28. The instrument according to claim 22, wherein the instrument tip hasa shaped end for mating with a workpiece.
 29. A trackable medicalinstrument for use in a computer assisted image guided surgery systemhaving a digitizer for tracking the position of the instrument in threedimensional space and a display providing an indication of the positionof the instrument with respect to images of a body part take takenpreoperatively, the instrument comprising: a guide member having anemitter array mounted thereon for being tracked by a digitizer; a driveshaft contained within the guide member, the drive shaft having alongitudinal axis and a proximal and a distal end, the drive shaft beingrotatable within the guide member while being fixable within the guidemember in a direction of the longitudinal axis; an instrument tipextending from the proximal end of the drive shaft; wherein theinstrument tip rotates freely relative to the guide member while beingfixable axially relative to the guide member; and a drive handleextending from the distal end of the drive shaft for guiding theinstrument, including the guide member, and for imparting rotary motionto the drive shaft and the instrument tip independent of the guidemember.
 30. The instrument according to claim 29, further comprising aproximal coupler for interchangeably coupling the drive source to thedrive shaft.
 31. The instrument according to claim 30, wherein theproximal coupler comprises a male-female socket joint disposed on thedrive shaft and the drive source to removably connect the drive sourceto the drive shaft.
 32. The instrument according to claim 29, whereinthe drive handle includes a ratchet.
 33. The instrument according toclaim 29, wherein the drive handle includes a motor for imparting rotarymotion to the drive shaft.
 34. The instrument according to claim 29,further comprising a distal coupler for interchangeably coupling theinstrument tip to the drive shaft.
 35. The instrument according to claim34, wherein the distal coupler includes a male-female socket jointdisposed on the drive shaft and the instrument tip to removably connectthe instrument tip to the drive shaft.
 36. The instrument according toclaim 29, wherein the instrument tip is an awl.
 37. The instrumentaccording to claim 29, wherein the instrument tip is a tap.
 38. Theinstrument according to claim 29, wherein the instrument tip has ashaped end for mating with a workpiece to be rotated by said driveshaft.
 39. The instrument according to claim 29, wherein the instrumenttip is a drill bit.
 40. The instrument according to claim 29, whereinthe emitter array includes at least one LED array for emitting lightsignals.
 41. The instrument according to claim 29, wherein the at leastone LED array includes a base and a plurality of LED emitters disposedon the base.
 42. The instrument according to claim 29, wherein at leastone bushing is provided in the guide member to reduce friction betweenthe guide member and drive shaft.
 43. A trackable medical instrument foruse in a computer assisted image guided surgery system having adigitizer for tracking the position of the instrument in threedimensional space and a display providing an indication of the positionof the instrument with respect to images of a body part takenpreoperatively, the instrument comprising: a guide member having atracking device mounted thereon for being tracked by a digitizer; adrive shaft contained within the guide member, the drive shaft having alongitudinal axis and a proximal and a distal end, the drive shaft beingrotatable within the guide member while being fixable within the guidemember in a direction of the longitudinal axis; an instrument tipextending from the proximal end of the drive shaft; wherein theinstrument tip rotates freely relative to the guide member while beingfixable axially relative to the guide member; and a drive handleextending from the distal end of the drive shaft for guiding theinstrument, including the guide member, and for imparting rotary motionto the drive shaft and the instrument tip independent of the guidemember.
 44. The instrument according to claim 43, wherein the trackingdevice includes a passive signal generator.
 45. The instrument accordingto claim 44, wherein the instrument comprises at least one reflectivesurface for reflecting signals to be tracked by the digitizer.
 46. Theinstrument according to claim 44, wherein the instrument comprises atleast three reflective surfaces for reflecting signals to be tracked bythe digitizer.
 47. The instrument according to claim 43, furthercomprising a proximal coupler for interchangeably coupling the drivesource to the drive shaft.
 48. The instrument according to claim 47,wherein the proximal coupler comprises a male-female socket jointdisposed on the drive shaft and the drive source to removably connectthe drive source to the drive shaft.
 49. The instrument according toclaim 43, further comprising a distal coupler for interchangeablycoupling the instrument tip to the drive shaft.
 50. The instrumentaccording to claim 49, wherein the distal coupler includes a male-femalesocket joint disposed on the drive shaft and the instrument tip toremovably connect the instrument tip to the drive shaft.
 51. A trackablemedical instrument for use in a computer assisted image guided surgerysystem having a digitizer for tracking the position of the instrument inthree dimensional space and a display providing an indication of theposition of the instrument with respect to images of a body part takenpreoperatively, the instrument comprising: a guide member having anemitter array mounted thereon for being tracked by a digitizer; and adrive shaft contained within the guide member, the drive shaft having alongitudinal axis and a proximal and a distal end, the drive shaft beingrotatable within the guide member while being fixable within the guidemember in a direction of the longitudinal axis, the proximal end of thedrive shaft having a first connector for receiving at least one drivesource for transmitting torque to the drive shaft causing rotation ofthe drive shaft relative to the guide member, and the distal end havinga second connector for receiving at least one instrument tip.
 52. Atrackable medical instrument for use with a surgical navigation system,the trackable medical instrument comprising: a surgical implement havinga distal end; a guide member coupled to the surgical implement; and atracking device mounted to the guide member, wherein the tracking deviceis rotatable relative to the surgical implement wherein the relationshipbetween the tracking device and the distal end of the surgical implementremains substantially constant upon rotating the tracking devicerelative to the surgical implement and the substantially constantrelationship enables the distal end of the surgical implement to betracked by the surgical navigation system.
 53. The trackable medicalinstrument as defined in claim 52, wherein the substantially constantrelationship between the tracking device and the distal end of thesurgical implement is a distance between the tracking device and thedistal end of the surgical implement.
 54. The trackable medicalinstrument as defined in claim 52, wherein the surgical implementcomprises a proximal end comprising a coupling member.
 55. The trackablemedical instrument as defined in claim 52, wherein the substantiallyconstant relationship enables both orientation in three-dimensionalspace of the surgical implement and a depth the distal end of thesurgical implement has been inserted into a body part to be tracked bythe surgical navigation system.
 56. The trackable medical instrument asdefined in claim 52, wherein the tracking device is fixed axially withrespect to the distal end of the surgical implement.
 57. The trackablemedical instrument as defined in claim 52, wherein the surgicalimplement is rotatably coupled to the guide member.
 58. The trackablemedical instrument as defined in claim 57, wherein the tracking deviceis fixedly secured to the guide member.
 59. The trackable medicalinstrument as defined in claim 52, wherein the surgical implement andthe guide member are integral.
 60. The trackable medical instrument asdefined in claim 52, wherein the tracking device is selected from atleast one of a LED, a reflector, an acoustic device, a magnetic device,an electromagnetic device, a radiologic device, a micropulsed radardevice or combinations thereof.
 61. The trackable medical instrument asdefined in claim 52, wherein the tracking device is one of either anactive tracking device or a passive tracking device.
 62. The trackablemedical instrument as defined in claim 52, wherein the surgicalimplement is selected from at least one of a tap, an awl, a drivinginstrument, a drill, or combinations thereof.
 63. The trackable medicalinstrument as defined in claim 52, further comprising a drive sourcecoupled to the guide member to drive the surgical implement.
 64. Thetrackable medical instrument as defined in claim 63, wherein the drivesource, the surgical implement and the guide member are integral. 65.The trackable medical instrument as defined in claim 63, wherein thedrive source is a drive handle.
 66. The trackable medical instrument asdefined in claim 65, wherein the drive handle includes a ratchet. 67.The trackable medical instrument as defined in claim 63, wherein thedrive source is a motor.
 68. The trackable medical instrument as definedin claim 63, further comprising a drive shaft housed within the guidemember, wherein the drive source is operable to rotate the drive shaftto rotate the surgical implement.
 69. The trackable medical instrumentas defined in claim 68, wherein the surgical implement and the drivesource are removable from the drive shaft.
 70. The trackable medicalinstrument as defined in claim 52, wherein the tracking device includesa plurality of tracking devices.
 71. The trackable medical instrument asdefined in claim 52, further comprising a sensor operable to sense aremoval and connection of the surgical implement to the medicalinstrument.
 72. The trackable medical instrument as defined in claim 52,further comprising a bushing operable to allow the tracking device to berotated relative to the surgical implement.
 73. The trackable medicalinstrument as defined in claim 72, wherein the bushing is positionedwithin the guide member.
 74. The trackable medical instrument as definedin claim 52, further comprising a plurality of surgical implements eachoperable to be interchangeably coupled to the guide member.
 75. Thetrackable medical instrument as defined in claim 52, wherein thetracking device includes a tracking array mounted to the guide member.76. The trackable medical instrument as defined in claim 52, wherein theguide member includes a mount for mounting the tracking device.
 77. Thetrackable medical instrument as defined in claim 76, wherein the guidemember further includes an elongated tubular body with the guide membermount extending from the elongated tubular body.
 78. A trackable medicalinstrument for use with a surgical navigation system, the trackablemedical instrument comprising: a surgical implement having a distal end;a guide member coupled to the surgical implement; a tracking devicemounted to the guide member; and a means for rotating the trackingdevice relative to the surgical implement; wherein the relationshipbetween the tracking device and the distal end of the surgical implementremains substantially constant upon rotating the tracking devicerelative to the surgical implement and the substantially constantrelationship enables the distal end of the surgical implement to betracked.
 79. The trackable medical instrument as defined in claim 78,wherein the surgical implement is rotatably coupled to the guide member.80. The trackable medical instrument as defined in claim 78, wherein thesurgical implement is integral with the guide member.
 81. The trackablemedical instrument as defined in claim 78, wherein the tracking deviceis fixed axially with respect to the distal end of the surgicalimplement.
 82. The trackable medical instrument as defined in claim 78,further comprising a drive source coupled to the guide member to drivethe surgical implement.
 83. The trackable medical instrument as definedin claim 78, wherein the tracking device is a passive reflectivetracking device and the medical instrument is a wireless instrument. 84.The trackable medical device as defined in claim 78, wherein thesurgical implement and the guide member extend along a longitudinalaxis.
 85. The trackable medical instrument as defined in claim 78,further comprising a sensor operable to sense a removal and connectionof the surgical implement to the medical instrument.
 86. A trackablemedical instrument for use with a surgical navigation system, thetrackable medical instrument comprising: a surgical implement having adistal end; a handle positioned near a proximal end of the medicalinstrument; a guide member coupled to the surgical implement and handle;and a tracking device mounted to the guide member, wherein the trackingdevice is rotatable relative to the surgical implement; and therelationship between the tracking device and the distal end of thesurgical implement remains substantially constant upon rotating thetracking device relative to the surgical implement.
 87. The trackablemedical instrument as defined in claim 86, wherein the handle is a drivehandle.
 88. The trackable medical instrument as defined in claim 86,wherein the surgical implement is selected from at least one of a tap,an awl, a driving instrument, a drill, or combinations thereof.